I am an operating department practitioner (ODP) who routinely
applies cricoid pressure under the direction of an anaesthetist in order
to prevent gastric aspiration. This article examines the current use of
cricoid pressure in anaesthetics.

During a recent learning experience I had an opportunity to perform
cricoid pressure on an electronic training aid which measured the
efficiency and the accuracy of the pressure applied. I found that it was
difficult to maintain the correct amount pressure and to apply this in
the correct position. Wayne-Conroy (2007) states that this is not
unusual and that practitioners are often surprised by the force that is
required. This startling discovery directed the choice of topic for this
article. Furthermore, the examination of the author's personal
practice lead to the questioning of the practice of colleagues. The
application of cricoid pressure is a technical skill and as such needs
to be practiced regularly to ensure correct position and pressure and
thereby patient safety.

Brisson & Brisson (2010) suggest that perioperative
practitioners often apply cricoid pressure incorrectly and this renders
it ineffective. Furthermore, Ewart (2007) states that the use of cricoid
pressure is indiscriminate and that there is little evidence to show
that it is beneficial to patient care. In this article I explore the
relevant research to establish current best practice, and to identify
the correct amount of pressure and the hazards which may occur when the
procedure is performed incorrectly. I also make recommendations which
aim to enhance professional practice.

Gastric aspiration or Mendelson's syndrome occurs when gastric
acid comes into contact with the lungs due to the absence of a cough
reflex (Ewart 2007). Patients undergoing a general anaesthetic are
predisposed to this as they have no protective mechanisms because their
state of consciousness is affected (Pattern 2006). When a patient is
conscious the epiglottis ensures that food is passed down the oesophagus
and not the trachea. In anaesthetised patients these laryngeal reflexes
are lost due to the administration of drugs such as induction agents and
muscle relaxants. If gastric contents are aspirated into the lungs it
may result in aspiration pneumonitis leading to extended ventilation and
admission to intensive care (Farman 2004).

Risk of gastric aspiration during anaesthesia

Whilst all patients who are receiving general anaesthesia are at
increased gastric aspiration (Pattern 2006), some patients fall into a
higher risk category. Any patient who suffers from increased gastric
volume or delayed gastric emptying is at risk from Mendelson's
syndrome (Kozial et al 2000). Simpson and Popat (2001) describe patients
at risk of aspiration as those that have experienced trauma which may
mean that they do not know when they last ate or drank, and patients who
suffer from hiatus hernias or reflux. Obstetric patients are at
particular risk due to an enlarged uterus and the physiological changes
that take place during pregnancy.

Cricoid pressure to prevent aspiration of gastric contents

Owen et al (2002) remarked that cricoid pressure can be seen in
medical literature from the 18th century. However, Sellick (1961) first
described its use in The Lancet. Prior to this the aspiration of stomach
contents was often fatal and in 1956 as many as 110 deaths during
anaesthesia were attributed to the aspiration of gastric content
(Wayne-Conroy 2007). Cricoid pressure or Sellick's manoeuvre is
used at induction of and occasionally at emergence from a general
anaesthetic. Prior to the introduction of Sellick's manoeuvre
anaesthesia was induced with the patient in an upright position
(Sinclair & Luxton 2005).

Cricoid pressure should only be applied by a skilled practitioner
(Enkin et al 2000). However, Sellick himself described the procedure as
a 'simple technique' and this description may well have lead
to a relaxed approach to teaching the skill. My personal opinion is that
this is not a simple skill to develop. Wayne-Conroy (2007) concurs that
it is a difficult technique to perfect and comments that in the past
there has not been enough training in this area of anaesthesia.

The aim of applying cricoid pressure is to exert pressure on the
cricoid cartilage to occlude the oesophagus, which then prevents the
regurgitation of stomach contents into the pharynx. The cricoid
cartilage can be found by locating the first firm bulge beneath the
Adam's apple (Stanton 2006). This is often easier to identify in a
male than a female because it is well defined however, if not obvious it
can be located by asking the patient to swallow before the anaesthetic
is commenced. This shows the Adam's Apple clearly and subsequently
the cricoid cartilage can be located.

Application of cricoid pressure

Cricoid pressure can be applied either with one hand - which allows
the assistant to aid the anaesthetist, or two handed - which is known as
Sellick's manoeuvre. Sellick's manoeuvre is performed by the
application of the left hand behind the patient's neck to prevent
the pressure undoing the flexion of the neck and allowing for
laryngoscopy. Farman (2004) comments that Sellick's manoeuvre must
be used in cervical spine injuries due to the support provided by the
second hand.

The right hand is normally used by practitioners in the UK due to
the design of the majority of anaesthetic rooms (Wayne- Conroy 2007).
However, in practice the author has an airway trolley which is mobile,
enabling pressure to be applied with either hand. Stanton (2006)
comments that researchers have found that practitioners can better judge
the amount of pressure that has been exerted with their right hand and
concluded that the right hand should be favoured.

By using one hand to perform this technique the practitioner is
performing a modification of Sellick's manoeuvre. As previously
mentioned, without the support of the other hand flexion is undone,
however in the author's experience it is rare that a second
practitioner is available to give support. It is evident there is a
theory practice divide.

Walsh and Ford (1998) suggest that there is a wide chasm between
how care should be carried out and how it actually is. The HPC (2008)
states that practitioners should adopt an evidence-based approach to
practice. This is defined as the use of the best clinical evidence to
make decisions for the care of patients with emphasis placed on evidence
which is obtained from disciplined research (Polit & Beck 2006).
Greenhalgh (2001) suggests that this is not merely the reading of papers
but it is the 'systematic framing' of questions relating to
the care of a patient and the ability to convert new evidence in
relation to sound patient care.

The cricoid cartilage is used because it is the only complete ring
of cartilage in the respiratory tract. The pressure is applied with the
right hand with the practitioner's thumb and fore finger (see
Figure1). However, there is debate about which fingers should be used.
Sellick (1961) advocated the use of the thumb and second finger, to
avoid deviating the trachea. Alternatively, Farman (2004) suggests that
the thumb and first two fingers should be used to apply an even
pressure. The information available is conflicting and there is no
definitive answer.

[FIGURE 1 OMITTED]

The use of pressure during Sellick's manoeuvre

The pressure should be applied in a downward motion without lateral
tracheal deviation (Farman 2004) and is maintained until the tracheal
tube is in place and the cuff is inflated. A force of 30 Newtons (N) is
applied and this is enough to prevent regurgitation (Kumar 2000).
However, the recommended amount of force which should be applied has
been a source of debate (Schmidt & Akeson 2001). Sellick originally
recommended as much force as was necessary, but it was later suggested
that the amount of pressure should be similar to that which would cause
pain across the bridge of the nose. Since the 1960s when Sellick carried
out his research, practitioners now view pain and respond to patients
differently. Pain is subjective: it is what the patient says it is.

Communication with the patient is paramount when applying cricoid
pressure due to the discomfort experienced by the patient. A clear
explanation of the procedure is also important as this can reduce
patient anxiety and panic.

The debate relating to the amount of pressure applied to the
cricoid cartilage is mainly due to one of the complications of cricoid
pressure which is the rupture of the oesophagus. Although this is a rare
event it can be fatal (Ewart 2007, Landsman 2004). Vanner et al (1992)
recommended a force of 40 N. However, further studies found that the
recommended force varied depending on the level of consciousness of the
patient (Farman 2004). Studies carried out using both live patients and
cadavers showed that in a conscious patient a force of 20 Newtons was
sufficient to protect against aspiration. In an unconscious patient this
could be increased to 30N or above (Haslam et al 2003). The type of
drugs used to induce anaesthesia are also a factor influencing how much
pressure should be exerted, and practitioners are advised to use a
common sense approach (Farman 2004). Farman (2004) comments that if
excessive pressure is exerted on a conscious patient then the gag reflex
is triggered.

Wayne-Conroy (2007) states that the pressure required should be
between 20 and 40N. Due to the large variation in recommended pressure
it is difficult for a practitioner to know what is the appropriate
amount of force to be exerted.

During the cricoid pressure training session I found that it is
difficult to maintain 30N of pressure and also to know how much pressure
is being applied. This can have implications for the patient: too little
pressure and the risk of gastric aspiration is increased but too much
pressure could cause unnecessary pain for the patient or a potential
risk to the oesophagus. The concern relating to the application of
pressure is echoed by Clayton and Vanner (2002). They found that in a
study of 40 experienced health practitioners only three were able to
maintain the correct amount of pressure for a period of one minute. In
the author's experience, difficult intubations can often take
longer than a minute.

I have found it difficult to ascertain exactly how much pressure is
being exerted. Stanton (2006) alluded to practitioners having
difficulties in converting the measurement of Newtons into actual
practice. What is perceived to be 30N by one practitioner might feel
entirely different to another. The measurement is not objective and
therefore, after review of current literature, the use of training
devices is advocated in order to allow practitioners to determine what
30N feels like and to correctly locate the cricoid cartilage.

Standardising practice

Stanton (2006) commented that there is a no standardised approach
to cricoid pressure and that this is due primarily to the amount of
debate on the correct amount of pressure that is needed for success. In
an age where standardisation and benchmarking are necessary for a gold
standard approach to practice, this should be paramount. Wayne-Conroy
(2007) remarks that there should be a priority for standardisation in
teaching this technique. Such standardisation could be developed through
the use of training aids to allow practitioners to develop competence in
the application of cricoid pressure.

Due to the lack of a definitive method of performing this technique
it is assumed that mentors pass on poor techniques to their students and
thereby perpetuate poor practice (Stanton 2006). Pattern (2006)
introduced an education programme which aimed to assess and improve
practitioners' skills in the application of cricoid pressure. It
was found that, before the programme, only two out of 51 anaesthetic
practitioners could locate the cricoid cartilage and maintain the
correct amount of pressure. However, after completing the course the
number was increased to 35. Pattern (2006) recommended that regular
updates were essential in maintaining this skill.

Effectiveness of Sellick's manoeuvre

The effectiveness of the application of the correct pressure in
reducing and preventing gastric aspiration has been questioned by
Gobindram and Clarke (2008). Ewart (2007) supported this opinion and
commented that Sellick based his study on assumptions. Wayne-Conroy
(2007) reinforced this view and commented that, even if cricoid pressure
is applied correctly, aspiration may still take place.

Sellick (1961) stated that the oesophagus is occluded between the
cricoid cartilage and cervical vertebra. However, studies that have been
carried out using CT and MRI imaging have shown that, instead of
occluding the oesophagus, it is displaced laterally (Smith et al 2003).
Ewart (2007) concluded that this may account for cricoid pressure being
unsuccessful.

Furthermore, Ewart (2007) commented that Sellick based his study on
the theory that pressure exerted on the cricoid cartilage increased
upper oesophageal sphincter pressure. However, this is not the case.
Regurgitation is prevented due to the lower oesophageal sphincter
pressure being lower than stomach pressure (Ewart 2007). The original
study was based on evidence that was up to date at the time, but the
procedure has not been updated since new evidence has been published
(Gobindram & Clarke 2008).

Although the effectiveness of Sellick's manoeuvre has been
questioned, Farman (2004) advocated the use of cricoid pressure and
commented that this is the leading method of preventing acid aspiration
in the UK. Although it is commonly used in the UK this is not the case
in France. The French neutralise the stomachs acid with the use of
antacids prior to theatre. The reduction of the pH of the stomach acid
is believed to reduce harm (Farman 2004).

Cricoid pressure can make laryngoscopy difficult due to altered
larynx anatomy (Arthurs 2001). Gobindram and Clarke (2008) commented
that often it causes airway obstruction and affects the success of
intubation. They further commented that, when cricoid pressure is
applied successfully, the anaesthetist will ask for less pressure to
pass the endo tracheal tube. In the experience of the author this has
often been the case and it is questionable to whether this negates the
success of the pressure as it is altered.

If indeed cricoid pressure is ineffective, as has been suggested,
then should there be an alternative method of preventing acid
aspiration? Wayne-Conroy (2007) commented that currently there is no
alternative. However, Gobindram and Clarke (2008) highlighted a study
carried out by Snow and Nun (1959) which looked at inductions using a
40[degrees] head tilt in place of the application of cricoid pressure.
The rationale for this position is that gastric contents could not reach
laryngeal level. It was found that in 606 high risk cases, only one
resulted in regurgitation and this was attributed to a low
administration of muscle relaxant. Although this research is dated there
are reasonable alternatives to cricoid pressure which are less painful
and are suggested to be more effective. By adopting Sellick's
manoeuvre as a protocol for rapid sequence induction, and with so little
importance being placed on doing it correctly, anaesthetic practitioners
could be accused of a blase attitude towards aspiration. Sellick (1961)
commented that the procedure could be taught to an assistant in a matter
of minutes (Lerman 2009).

Conclusion

It is evident that there is much debate concerning this area of
clinical practice. Furthermore, there is doubt regarding its validity in
protection against Mendelson's syndrome. However, it is the opinion
of the author that if the medical profession continues to use this form
of practice, then standardisation and training should be a matter of
priority due to the potential risk to the patient if the manoeuvre is
performed incorrectly.

The author found the use of an electronic cricoid pressure training
device to be a beneficial experience.. The primary recommendation of
this article is that more training is required in relation to this
technique and the use of the aforementioned device is highly
recommended. There are alternatives to the electronic trainer which are
viewed to be more cost effective. Matthews (2001) used a 5ml Luer-lock
syringe. It was found that compression of the syringe to the 17mm point
was found to be the equivalent to 30N of pressure.

The debate and subsequent doubt regarding the effectiveness of
cricoid pressure leads to the questioning of the decisions made
regarding patient care. The author is not the first after viewing the
current literature to suggest that it could be an out dated practice.
From this limited view there appears to be much debate surrounding the
practice and its correct application and that it requires development
and standardisation. The Health Professions Council (2008) requires ODPs
to adhere to standards of proficiency which ensure that the professional
interprets new information in order to make professional judgments and
change practice. This article is by no means exhaustive, however from
analysing the literature we are duty bound to influence a change in
practice by questioning what we are asked to do.